A reflection on recent efforts in optimization of cooling capacity of electrocaloric thin films

Abstract

Despite the advantages of electric field efficiency and miniaturization, the limited operating temperature range and mediocre cooling efficiency of electrocaloric thin films represent the key obstacles to their practical applications in cooling advanced electronics. In this review, we discussed the current efforts and challenges facing the development of high-performance electrocaloric thin films and explored universal approaches along with their physical mechanisms for optimizing the electrocaloric response in thin films. We first emphasize the significance of the indirect method for determining the electrocaloric effect (ECE) in thin films and restate the conditions for the application of Maxwell’s equations. Particularly, we flag a couple of common artifacts of the electrocaloric results induced by the indirect method in recent attempts at the optimization of the ECE. We then cover chemical modification, interface engineering, and strain engineering as effective routes to improve the adiabatic temperature change (ΔT), reduce the driving electric field (E), and widen the operating temperature range (Tspan). At last, we propose that slush relaxors can be exploited as the base system for simultaneously achieving large ΔT, broad Tspan, and low E. Furthermore, we also discuss that the employment of high-entropy oxide perovskites is a feasible approach for greatly raising the dipolar entropy change under low electric fields. At last, we stress the significance and pressing need to measure the EC parameters of thin films with reliable direct methods. We hope that the high-performance electrocaloric thin films and the design rationale discussed in this review could inspire more facile and novel methods to achieve a better electrocaloric response.